Fourteen hyperactive boys were treated with up to 15mg/day of clorgyline, parnate or deprenyl (10 mg/day), selective and non-selective Monoamine Oxidase Inhibitors, or amphetamine (0.5/mg/kg). The major findings were that both the selective (clorgyline) and non-selective (tranylcypromine) MAOIs were efficacious in reducing restless and inattentive behaviors. Currently, a trial of 1-deprenyl in low dose (10 mg/day) and high dose (30 mg/day) is underway. The aim of the study is to elucidate the neurotransmitter mechanisms mediating stimulant drug effects in hyperactivity.